1. Field of the Invention
The present invention relates to a jig for headpiece aggregate machining and a method for manufacturing a thin-film magnetic head.
2. Discussion of Background
A thin-film magnetic head is manufactured through processes in which a plurality of thin-film magnetic head elements are arrayed in a lattice-like pattern on a wafer constituted of a ceramic substrate. A row-like head piece aggregate is taken out of the wafer and the row-like head piece aggregate thus taken out is bonded to a jig with adhesive and then lapped. One of the main objects of the lapping process is to set the throat height (gap depth), which greatly affects the electromagnetic characteristics. A thin-film magnetic head is provided with pole pieces facing opposite each other across a gap film, and yoke portions that are continuous with the pole pieces. One of the pole pieces is provided with a displacement area that rises in a direction that separates it from the surface of the ceramic substrate, which is located behind the front end area, which is formed in such a manner that it lies practically parallel to the surface of the ceramic substrate. The pole piece is continuous with the yoke portion via the displacement area. The depth of the pole pieces from the front end to the displacement point is normally referred to as the throat height or the gap depth. The throat height is a micro dimension of, for instance, approximately 1 .mu.m and it plays an extremely important role in determining the electromagnetic characteristics. In setting the throat height, a row-like head piece aggregate that has been cut out from the wafer is bonded with adhesive to a jig constituted of iron, stainless steel or the like, and in this state, the end surface where the pole piece emerges is lapped to a specific point in order to attain a specific throat height for the row-like head piece aggregate. Lapping technologies of the known art for a head piece aggregate are disclosed in Japanese Unexamined Patent Publication (Kokai) No. 95716/1987 and Japanese Unexamined Patent Publication (Kokai) No. 113818/1988.
However, since the coefficients of thermal expansion differ between the head piece aggregate, which is constituted of a ceramic structure, and a jig, which is constituted of iron, stainless steel or the like, distortions are generated in the head piece aggregate due to this difference in the coefficients of thermal expansion, causing a bow or bend in the head piece aggregate. A bow or bend in a head piece aggregate is also caused by hardening contraction of the adhesive used for attaching the head piece aggregate to the jig. This makes it difficult, during the lapping process and the like, to perform lapping in such a manner that the throat heights of the various electromagnetic elements arrayed on the head piece aggregate are the same.
Attempts to solve the problem discussed above have already been made. For instance, Japanese Unexamined Patent Publication (Kokai) No. 71415/1990 discloses a technology with which the throat height is controlled precisely by constituting the upper portion and the lower portion of the lap carrier to which the head piece aggregate is temporarily bonded, with materials whose coefficients of thermal expansion are different from each other, temporarily bonding the head piece aggregate and the lap carrier with a thermally soluble adhesive and by ensuring that during this temporary bonding, the lap carrier surface that comes in contact with the head piece aggregate becomes bowed when heated and that the lap carrier surface regains its flatness when cooled. Also, Japanese Unexamined Patent Publication (Kokai) No. 291010/1992 discloses a technology with which thin-film magnetic heads with consistent throat height accuracy can be obtained by controlling the machining distortions on the front surface (floating surface) and the rear surface of the head piece aggregate by means of deforming the head piece aggregate in such a manner that the distortion in the front surface and in the rear surface of the head piece aggregate cancel each other out, or by a means of lapping with differing degrees of machining distortion.
However, none of the technologies in the prior art disclose a means for correcting distortions of the head piece aggregate which occur after it is secured on to the jig.